Heart disease is the leading cause of death in the United States, and half of those deaths are sudden and unexpected, occurring within an hour of onset of symptoms. Cardiac arrhythmias can lead to sudden death, and have been strong risk factors in epidemiologic studies. The value of screening for and treating disturbances of cardiac rhythm is uncertain, however, since recent trials of antiarrhythmic drugs have shown potential harm. Many physicians are now turning to implantible cardiac defibrillators (ICD's), which are now easy to implant and effective at converting arrhythmia despite the cost of over $30,000 each, ICD's are poised for explosive growth in use to treat patients at risk of sudden death. The purpose of the Cardiac Arrhythmia PORT is to develop a comprehensive decision model for the screening and treatment of patients at risk for sudden cardiac death that incorporate information about a range of outcomes (mortality, morbidity, functional status, quality of life, and cost) as well as patient preferences. To accomplish this overall goal, we will perform six inter-related projects: l) use administrative data to document costs of arrhythmia management, and factors that affect variations in practice patterns and cost; 2) perform a nested case-control study to determine specific risk factors for, sudden cardiac death; 3) synthesize the literature about the efficacy of antiarrhythmic management and other forms of cardiac therapy on sudden death; 4) document in a prospective patient cohort the effectiveness of alternative management strategies on a broad array of outcomes, including functional status, quality of life, and cost; 5) determine patient values and preferences relevant to management decisions, and examine how these factors affect the effectiveness of antiarrhythmic management; and 6) construct a decision model that incorporates data on medical effectiveness and preferences and that will support clinical management recommendations to translate these research finding into clinical practice.